v3.25.2
Fair Value Measurement - Schedule of Change in Fair Value of Derivative Warrant Liabilities (FY) (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2025
Dec. 31, 2024
Dec. 31, 2023
Warrant Liabilities      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Beginning balance $ 199,645 $ 70,930 $ 3,887
Additions   0 1,716
Adjustment to fair value (26,837) 128,715 68,334
Settlements   0 (3,007)
Ending balance 0 199,645 70,930
Bifurcated Embedded Derivative Liabilities      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Beginning balance 0 386,469 4,901
Additions   0 20,829
Adjustment to fair value   627,263 360,739
Settlements   (1,013,732) 0
Ending balance   0 386,469
Power Purchase Agreements - Liability      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Beginning balance 444 0 0
Additions   770 0
Adjustment to fair value (17) (326) 0
Settlements   0 0
Ending balance 427 444 0
Series B Tranche Liability      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]      
Beginning balance 0 69,648 0
Additions   0 10,300
Adjustment to fair value   (49) 104,879
Settlements   (69,599) (45,531)
Ending balance   0 69,648
Power Purchase Agreements - Asset      
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Beginning balance 2,562 1,459 0
Additions   0 1,040
Adjustment to fair value 882 1,103 419
Settlements   0 0
Ending balance $ 3,444 $ 2,562 $ 1,459